Multi-speed transmission free wheel for a bicycle

ABSTRACT

In a multi-speed transmission free wheel to be provided on a wheel hub rotatably mounted on a wheel shaft of a bicycle are included a plurality of sprocket wheels respectively having a different number of teeth. Each tooth of said sprocket wheels has its peripheral portion that faces to a lowest speed transmission sprocket wheel and is notched in a manner that the foremost end thereof is deviated toward a highest speed transmitting sprocket wheel so that when the driving chain to be driven by treading the pedals, the shifting operation can be effected smoothly and exactly despite of a big difference in tooth number between said two sprocket wheels.

United States Patent [191 Nagano MULTI-SPEED TRANSMISSION FREE WHEEL FORA BICYCLE [76] Inventor: Masashi Nagano, c/o Shimano Industrial Co.,Ltd., No. 77, 3-cho, Sakai, Japan [22] Filed: Aug. 13, 1971 [21] Appl.No.: 171,526

[30] Foreign Application Priority Data 3,478,614 11/1969 Shimano.....

FOREIGN PATENTS OR APPLICATIONS 5/1948 France 74/217 B Nov. 20, 1973Primary ExaminerLeonard l-l. Gerin Assistant Examiner--Frank l-l.McKenzie, Jr. Attorney-Moonray Kojima 57 ABSTRACT In a multi-speedtransmission free wheel to be provided on a wheel hub rotatably mountedon a wheel shaft of a bicycle are included a plurality of sprocketwheels respectively having a different number of teeth. Each tooth ofsaid sprocket wheels has its peripheral portion that faces to a lowestspeed transmission sprocket wheel and is notched in a manner that theforemost end thereof is deviated toward a highest speed transmittingsprocket wheel so that when the driving chain to be driven by treadingthe pedals, the shifting operation can be effected smoothly and exactlydespite of a big difference in tooth number between said two sprocketwheels.

3 Claims, 7 Drawing Figures PAIENTEUNBY 20 ms SHEET 10F 3 HTTJKNEYPAIENTEBRUYZO ma 3.772.932

sum 20F 3 FIGA //Vl/EN TOR MASRSHI NMAMJ an; ,6 Amway MULTI-SPEEDTRANSMISSION FREE WHEEL FOR A BICYCLE The present invention relates tothe multi-speed transmission free wheel for a bicycle that comprises aplurality of sprocket wheels respectively having a different number ofteeth, and more particularly it relates to such a multi-speedtransmission free wheel that is provided on a wheel hub so mounted as torotate about a shaft of the rear wheel and transmits multiple speeds tothe wheel hub together with an externally housed gear-shifting system ofa well-known type.

Conventionally it is a matter of common knowledge that a plurality ofsprocket wheels respectively provided with a different number of teethare mounted in a unidirectionally rotable manner on a wheel hub held onthe shaft of a bicycle wheel, and one of these sprocket wheels isselected by an externally housed gear-shifting system mounted adjacentthereto, thereafter the driving chain to be driven by the pedals isengaged with the teeth of the sprocket wheel thus selected therebyrendering it to change the speed of a bicycle.

The above-mentioned type of externally housed gearshifting system isprovided with an induction wheel which holds the driving chain in aninduceable manner and moves in the axial direction of the wheel hub sothat the induction wheel is operationally moved in said axial directionand the driving chain held thereby is brought into engagement with oneof the sprocket wheels disposed in said axial direction whereby therotation of the wheel is changed in relation to the driving speed of thedriving chain.

Referring to the sprocket wheels which is adapted for a multi-speedtransmission free wheel and employed in combination with theabove-mentioned externally housed gear-shifting system, the differencein tooth number between a maximum diameter sprocket wheel and a minimumdiameter sprocket wheel has become so great in recent years that amaximum diameter sprocket wheel has, for example, thirtytwo teeth or asmany as 34 teeth whereas a minimum diameter sprocket wheel has 14 teethonly. Moreover, such a difference is becoming greater and greater in theinversely geometrical manner.

The above-mentioned fact that a bigger difference in number between theteeth of the two sprocket wheels brings about a greater speed ratio is,on the one hand, sufiicient enough to provide an advantage that abicycle can be easily gear-shifted into any desired speed especiallywhen being driven on a road or down along the incline, but being, on theother hand, accompanied with a disadvantage that the driving chain isnot readily engageable with a sprocket wheel having selected teeth bymovement of the aforesaid induction wheel so that no exact and promptspeed changing operation can be accomplished. In other words, theengagement of the driving chain is normally made on the side into whichthe chain comes to start engaging with a selected sprocket wheel sothat, though the chain is forced on said side to move in the axialdirection by means of the induction wheel, yet on the side from whichthe chain disengages out of an original sprocket wheel, it remains asengaged as ever with the latter sprocket wheel since there is noparticular means to forcibly release the engagement of the driving chainwith the latter sprocket wheel. The result is that the driving chainruns aslant as shown in FIG. 1 and may very often get twisted betweensaid two sprocket wheels. This trouble is apt to take place generally inthe case that the difference in tooth number between the maximumdiameter sprocket wheel and the minium diameter sprocket wheel isexessively great and that said difierence is increased in the inverselygeometric series. Such a trouble will be more often experiencedespecially when the gear-shifting operation of the driving chain is madefrom the minimum diameter sprocket wheel directly to the maximumdiameter sprocket wheel. The cocurence of trouble is attributable to thefacts that firstly the driving chain is forcibly twisted when beinggearshifted as described above, secondly it is not engageable with asprocket wheel just next to the minimum diameter sprocket wheel becauseit is spaced from the other intermediate sprocket wheels, and lastly itskates on said sprocket wheel partly because it is forcibly moved in theaxial direction by means of the induction wheel even though it will moveto said sprocket wheel and partly because the sprocket wheels ofwell-known types are generally provided on the edges of their tee withonly a few or none of holds.

The present invention has been devised to eliminate the above-mentioneddisadvantages. Accordingly, an object of this invention is to provide amulti-speed transmission free wheel for a bicycle that is free from theabove-mentioned disadvantages and can always effeet the gear-shiftingoperation in a prompt and smooth manner. Another object of the inventionis to provide a multi-speed transmission free wheel for a bicycle thatis simple in structure, produceable in an easy manner and less expensivethan the conventioal ones. Further object of the invention is to providean improved type of multi-speed transmission free wheel for a bicycle,in which a difference in tooth number between a maximum diametersprocket wheel and a minimum diameter sprocket wheel is made excessivelygreat without limiting the number of teeth therebetween therebyproducing an effective speed shifting ratio.

While an embodiment of the invention will now be described, by way ofexample, with reference to the accompanying drawings, the novel featuresand construction of the present invention are as defined in the appendedclaims.

IN THE DRAWINGS,

FIG. 1 is a front view showing an example of the multispeed transmissionfr'ee wheel embodying the present invention;

FIG. 2 is a vertical cross section taken on the line of 11 11 thereof;

FIG. 3 is a plan view thereof;

FIG. 4 showing is a cross-sectional view showing extensively the toothportion of each sprocket wheel;

FIG. 5 is an enlarged vertical cross section showing a part of FIG. 3;

FIG. 6 is likewise an enlarged vertical cross section showing a part Bof the same; and

FIG. 7 is a front view partially showing a state where the free wheelmechanism embodying the invention is actually mounted on a bicycle.

In the present embodiment are applied 14 teeth to the first or minimumdiameter sprocket wheel 1, 17 teeth to the second sprocket wheel 2, 20teeth to the third or middle sprocket wheel 3, 24 teeth to the fourthsprocket wheel 4 and 28 teeth to the last or maximum diameter sprocketwheel 5.

Incidentally, each number of the teeth mentioned above may be changed asfreely as desired in such a manner, e. g., that a greater speed ratio,if desired, is obtained merely by increasing the tooth number of themaximum diameter sprocket wheel 5. In addition, the piece number of saidsprocket wheels if also freely changeable so that any desired piecenumber thereof can be selected in accordance with a desired speedtransmission range. Thus it is not to be limited exclusively up to thefive speed transmission free wheel described herein.

As is clearly evident in FIG. 2, the free wheel is adapted to be used bymounting the same on a rear hub 11 which is rotatably mounted on a hubspindle 13 secured to a bicycle frame member 12, comprising acylindrical hub spindle portion 11a sleeved onto said hub spindle 13 andtwo opposed hub cones 11c, 11d respectively including flange b (notshown) for supporting one end of each spoke. On the outer periphery ofthe hub cone 11d (at the right in FIG. 2) are formed screw means throughwhich the free wheel 10 is to be fixedly mounted to the hub cone 11d.The free wheel 10 to be mounted to the rear hub 11 in the abovementionedmanner consists of a driven member 6 having tapped portions 14engageable with said screw means provided on the outer periphery of thehub cone 1 1d, a driving member 7 sleeved to the outer periphery of saiddriven member 6 at regularly spaced apart intervals, said plurality ofsprocket wheels 1 to 5 to be secured to the outer periphery of saiddriving member 7 in equally spaced relation, a ball 8 interposed betweensaid members 6 and 7 for rotating them in relative direction, and aratchet mechanism 9 for transmitting from the driving member 7 to thedriven member 6 the forward driving force only that is transmitted fromany selected one of said sprocket wheels 1 to 5.

Said ratchet mechanism 9 cmprises a pawl member 9a which is forced inthe intermediate inner peripheral portion of said driven member 6 insuch a position as to correspond to said pawl member 9a, being normallypressed to engage therewith by means of a ring spring 90.

When the driving member 7 rotates in the forward driving direction, theforce thereof is transmitted to the driven member 6 through means ofsaid pawl members 9a and 9b engaged with each other, whereas when thedriving member 7 rotates in the rearward driving direction, the forcethereof is not transmitted to the driven member 6 since pawl pawl member9b skates on the pawl member 9a. Therefore, it is understood that whenthe force of driving a bicycle in the forward direction is transmittedto the driving member 7 to thereby move the same, the driven memer 6 isalso moved in synchronism through said ratchet mechanism 9 whereby therear wheel is rotated through the spokes secured to the rear hub 11,thus resulting in driving the bicycle.

The rotary movement of the driving member 7 is made possible by adriving mechanism portion 15 which is driven by the actuation of pedals(not shown) and a driving chain 16 which engages with any selected oneof the sprocket wheels 1 to 5 secured to the drivng member 7 andtransmits the driving force of said driving mechanism 15 to saidselected sprocket wheel as shown in FIG. 7.

Said driving mechanism portion 15 comprises a pair of cranks 17 whichrespectively have their foremost ends provided with a pedal and a frontgear 19 which is secured to crank shaft 18. Between said front gear 19and said selected sprocket wheel there is extended the driving chainl6.-Thus if the cranks 17 are rotated by treading the pedals, the frontgear 19 is rotated to move the driving member 7 through the drivingchain 16 and said selected sprocket wheel.

In order to engage the driving chain 16 with any selected one of saidsprocket wheels 1 to 5, use is made of such an externally housedgear-shifting sprocket 20 as is shown in FIG. 7. Said system 20 ismounted externally of the free wheel 10 on one end of the hub spindle 13secured to the bicycle frame member 12 and comprises an induction wheel20a which is movable in parallel to the axial direction of the hubspindle 13, a moving element 20b which is provided with a pantographmeans for moving said induction wheel 20a in parallel direction and awire operating mechanism 200 which consists of a release wire for movingsaid moving element 20b.

Said system 20 is used by extending the driving chain 16 on theinduction wheel 20a, in which the latter wheel 20a is moved through themoving element 20b by the operation of the wire operating mechanism 200whereby the driving chain 16 extended on the induction wheel 20a isinduced toward said plurality of sprocket wheels 1 to 5 to engage withany desired one thereof.

The above-mentioned free wheel 10, the use and operational conditionsthereof are all conventionally well known and devoid of novel features.

According to the present invention, said free wheel 10 consists of thesprocket wheels 1 to 5 of which, excepting the minimum diameter sprocketwheel 5, the intermediate sprocket wheels 2 to 4 are all provided withsuch tooth edges as shown extensively in FIG. 4 for the purpose ofclarity.

For a fuller understnding, there are formed notches 26 on the peripheralportions of the tooth edges of the sprocket wheels 2 to 4 which face tothe side where speed is to be reduced, that is, to the maximum diametersprocket wheel 5. The notched tooth edges are substantially inclined tothe side where speed is to be increased, that is, toward the minimumdiameter sprocket wheel 1, and the inner position of each inclined toothedge 27 is formed to be a levelled portion 28.

While reference has been made in the above embodiment to the threesprocket wheels 2 to 4 arranged in the intermediate positions, such aconstruction is also possible for the sprocket wheels 1 and 5 arrangedon both sides.

The sprocket wheels 1 to 5 located on both sides of the intermediatesprocket wheels 2 to 4 are located in the terminal positon for thedriving chain 16 when it is gear-shifted so that they need not be formedinto the shape as above mentioned, but may be formed into such a shapefor example as shown in FIGS. 5 and 6. Thus when the driving chain 16 isto be gear-shifted from the sprocket wheel 1 onto the sprocket wheel 5by the operation of the externally housed gear-shifting system 20, it ismoved to the sprocket wheel 5 at the side into which it comes; but onthe other hand, it will still stay on the sprocket wheel 1 at the sidefrom which it goes out so that the driving chain 16 is forced to runaslant as shown in FIG. 3. However, the tooth ends of the second minimumdiameter sprocket wheel 2 located next to said sprocket wheel 1 beingformed into the above-mentioned shape, the driving chain 16 runningaslant is exactly detained by these deviated tooth ends 27 and broughtinto engagement with the second sprocket wheel 2 without skatingthereon. In other words, said tooth ends of the sprocket wheel 2 areengageable with the first sprocket wheel 1 all the more readily becausethey are substantially deviated toward the latter sprocket wheel 1 sothat they can promptly and exactly engage with the driving chain 16.

Due to this engagement of tooth ends, the driving chain 16 that willretain its position on the first sprocket wheel 1 is forcibly draggedinto the second sprocket wheel 1 and moved in the axial directionthereof. Then, the driving chain 16 is moved therefrom to the similarlytooth-shaped sprocket wheels 3 and 4, one after another, until itreaches the last or minimum diameter sprocket wheel 5 thereby making itpossible to effect the gear-shifting operation of the driving chain 16from a high speed into low.

Likewise, the operation of shifting the driving chain from a low speedinto high is easily accomplished merely by moving said chain from thelast sprocket wheel to the first sprocket wheel via the intermediatesprocket wheels. To be more precise, the driving chain 16 is firstly puton the levelled portion 28 of the psrocket wheel 4, secondly on that ofthe sprocket wheel 3 and thirdly on that of the sprocket wheel 2 inturn, thereafter being brought into engagement with the deviated toothedges 27 of these sprocket wheels in the same order that it has been putthereupon.

Therefore, it is to be noted that the multi-speed transmission freewheel in accordance with the present invention can effect a prompt andsmooth gear-shifting operation of the driving chain into any desiredspeed rate thereby attaining the purposes of eliminating all thedeficiencies that are conventionally caused by the retardation of thespeed changing operation and effecting the safe and exact speed changingoperation of a bicycle.

It is believed that many advantages of a multi-speed transmission freewheel embodying the present invention will be readily understood, andalthough preferred embodiments are as illustrated and described, it isalso to be noted that further modifications and arrangement of parts maybe resorted to which will fall within the purview of the invention asclaimed.

What is claimed is:

l. A multispeed transmission free wheel for a bicycle to be mounted on awheel hub rotatably supported on a wheel shaft comprising a. a drivenmember secured to one end of said free wheel and rotatable along withsaid free wheel;

b. a cylindrically shaped driving member sleeved on the outer peripheryof said driven member at regularly spaced apart intervals, and rotatablein one direction with respect to said driven member while beingrotatable in the other direction integrally therewith;

c. a driving force transmitting mechanism for transmitting the force ofsaid driving member in the space between said driven member and saiddriving member; and

d. a plurality of different dent numbered sprocket wheels rigidly fixedon the outer periphery of said driving member at regularly spaced apartintervals, comprising addenda of each sprocket wheel opposed to agreater dent-numbered lower speed sprocket wheel are cut aslant from theouter periphery toward the radius thereof so as to form a flank facedeviated toward a less dent-numbered, higher speed sprocket wheel,further said addenda being cut at a right angle with the axis thereof soas to form each flat surface area defining a notched portion with saiddeviated flank face.

2. The arrangement of claim 1, wherein at least one of the sprocketwheels between the highest and lowest speed sprocket wheels is providedwith dents whose addenda are formed as set forth in item (d) of claim 1.

3. The arrangement of claim 2, wherein the addenda of said maximumdent-numbered, lowest speed sprocket wheel opposing to higher speedsprocket wheels are cut aslant with respect to the axis of said sprocketwheel.

1. A multispeed transmission free wheel for a bicycle to be mounted on a wheel hub rotatably supported on a wheel shaft comprising a. a driven member secured to one end of said free wheel and rotatable along with said free wheel; b. a cylindrically shaped driving member sleeved on the outer periphery of said driven member at regularly spaced apart intervals, and rotatable in one direction with respect to said driven member while being rotatable in the other direction integrally therewith; c. a driving force transmitting mechanism for transmitting the force of said driving member in the space between said driven member and said driving member; and d. a plurality of different dent numbered sprocket wheels rigidly fixed on the outer periphery of said driving member at regularly spaced apart intervals, comprising addenda of each sprocket wheel opposed to a greater dent-numbered lower speed sprocket wheel are cut aslant from the outer periphery toward the radius thereof so as to form a flank face deviated toward a less dent-numbered, higher speed sprocket wheel, further said addenda being cut at a right angle with the axis thereof so as to form each flat surface area defining a notched portion with said deviated flank face.
 2. The arrangement of claim 1, wherein at least one of the sprocket wheels between the highest and lowest speed sprocket wheels is provided with dents whose addenda are formed as set forth in item (d) of claim
 1. 3. The arrangement of claim 2, wherein the addenda of said maximum dent-numbered, lowest speed sprocket wheel opposing to higher speed sprocket wheels are cut aslant with respect to the axis of said sprocket wheel. 